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Title: Sp1149. II. Spectroscopy of H ii Regions near the Critical Curve of MACS J1149 and Cluster Lens Models
Abstract Galaxy-cluster gravitational lenses enable the study of faint galaxies even at large lookback times, and, recently, time-delay constraints on the Hubble constant. There have been few tests, however, of lens model predictions adjacent to the critical curve (≲8″) where the magnification is greatest. In a companion paper, we use the GLAFIC lens model to constrain the BalmerL–σrelation for Hiiregions in a galaxy at redshiftz= 1.49 strongly lensed by the MACS J1149 galaxy cluster. Here we perform a detailed comparison between the predictions of 10 cluster lens models that employ multiple modeling assumptions with our measurements of 11 magnified, giant Hiiregions. We find that that the models predict magnifications an average factor of 6.2 smaller, a ∼2σtension, than that inferred from the Hiiregions under the assumption that they follow the low-redshiftL–σrelation. To evaluate the possibility that the lens model magnifications are strongly biased, we next consider the flux ratios among knots in three images of Sp1149, and find that these are consistent with model predictions. Moreover, while the mass-sheet degeneracy could in principle account for a factor of ∼6 discrepancy in magnification, the value ofH0inferred from SN Refsdal’s time delay would become implausibly small. We conclude that the lens models are not likely to be highly biased, and that instead the Hiiregions in Sp1149 are substantially more luminous than the low-redshift BalmerL–σrelation predicts.  more » « less
Award ID(s):
1908823 2308051
PAR ID:
10514277
Author(s) / Creator(s):
; ; ; ; ;
Publisher / Repository:
AAS
Date Published:
Journal Name:
The Astrophysical Journal
Volume:
967
Issue:
2
ISSN:
0004-637X
Page Range / eLocation ID:
92
Format(s):
Medium: X
Sponsoring Org:
National Science Foundation
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